Pathogenesis and diagnosis of Shiga toxin-producing Escherichia coli infections

Characterization of Shiga Toxin-producing Escherichia coli Isolated from Cattle Around Ulaanbaatar City, Mongolia

Shiga toxin-producing Escherichia coli (STEC) are associated with severe infections including hemorrhagic colitis and hemolytic uremic syndrome in humans. Ruminants are known as reservoirs of STEC; however, no data are available on STEC in ruminants in Mongolia, where more than 5 million cattle and 25 million sheep are raised. To disclose the existence and characteristics of STEC in Mongolia, in this study, we isolated and characterized STEC from cattle in Mongolia. We collected 350 rectal swabs of cattle from 30 farms near Ulaanbaatar city and isolated 45 STEC from 21 farms. Rectal swabs were precultured with modified Escherichia coli broth and then inoculated to Cefixime-Tellurite Sorbitol MacConkey agar plate and/or CHROMagar STEC agar plate for the isolation of STEC. The isolation ratios in each farm were from 0% to 40%. Multiplex PCR for the estimation of O- and H-serotypes identified 12 O-genotypes (Og-types) and 11 H-genotypes (Hg-types) from 45 isolates; however, Og-types of 19 isolates could not be determined. Stx gene subtyping by PCR identified 2 stx1 subtypes (1a and 1c) and 4 stx2 subtypes (2a, 2c, 2d, and 2g). Forty-five isolates were divided into 21 different groups based on the Og- and Hg-types, stx gene subtypes and the existence of virulence factors, ehxA, eae, and saa, which includes several major serotypes associated with human illness such as O26:H11 and O157:H7. The most dominant isolate, OgUT:H19 [stx1a (+), stx2a (+), ehxA (+) and saa (+)], was isolated from eight farms. This is the first report on the characterization of STEC in cattle in Mongolia, and the results suggest the importance of further monitoring of STEC contamination in the food chains as well as STEC infection in humans.

Determining the prevalence of Escherichia coli, Salmonella, and shiga toxin-producing Escherichia coli in manure of dairy lagoons

AIM

The aim of this study was to determine the prevalence of microbial pathogens in manure of dairy lagoons in California.

METHODS AND RESULTS

To determine pathogens in dairy manure stored in anaerobic lagoons of dairy farm, an extensive field study was conducted across California to sample manure from 20 dairy farms. Samples were analyzed to determine the prevalence of indicator Escherichia coli, Shiga toxin producing E. coli (STEC), Salmonella, and E. coli O157: H7. To test the E. coli, STEC, and Salmonella, we used agar culture-based method followed by polymerase chain reaction (PCR) method. In addition, a real- time PCR based method was used to determine the presence of E coli O157: H7. Study demonstrated that the prevalence of Salmonella in manure sample is lower than E. coli. The presence of Salmonella was found in 2.26% of the samples, and both the culture-based and PCR methods yielded comparable outcomes in detecting Salmonella. Moreover, ∼11.30% of the total samples out of the 177 were identified as positive for STEC by qPCR.

CONCLUSION

These findings demonstrate that indicator E. coli are abundantly present in anaerobic lagoons. However, the presence of STEC, and Salmonella is substantially low.

Acquisition of plasmids from Shiga toxin-producing Escherichia coli strains had low or neutral fitness cost on commensal E. coli

Although it has been hypothesized that the acquisition of plasmids-especially those bearing virulence factors and antimicrobial resistance genes-increases the energetic burden and reduces the fitness of a bacterium in general, some results have challenged this view, showing little or no effect on fitness after plasmid acquisition, which may lead to change in the view that there are evolutionary barriers for a wide spread of such plasmids among bacteria. Here, to evaluate the fitness impact of plasmid-encoded antibiotic resistance and virulence genes, plasmids from O26:H11, O111:H8, and O118:H16 Shiga toxin-producing Escherichia coli (STEC) human and bovine isolates were transferred to the non-virulent E. coli HS and K-12 MG1655 strains. Sequencing and PCR were used to characterize plasmids, and to identify the presence of antimicrobial resistance and/or virulence genes. The fitness impact of plasmids encoding virulence and antimicrobial resistance upon bacterial hosts was determined by pairwise growth competition. Plasmid profile analysis showed that STEC strains carried one or more high and low molecular weight plasmids belonging to the B/O, F, I, K, P, Q, and/or X incompatibility groups encoding virulence genes (SPATE-encoding genes) and/or antimicrobial resistance genes (aadA1, strAB, tetA, and/or tetB). Competition experiments demonstrated that the biological cost of carriage of these plasmids by the commensal E. coli strain HS or the laboratory strain E. coli K-12 MG1655 was low or non-existent, ranging from - 4.7 to 5.2% per generation. This suggests that there are few biological barriers-or, alternatively, it suggests that there are biological barriers that we were not able to measure in this competition model-against the spread of plasmid encoding virulence and resistance genes from STEC to other, less pathogenic E. coli strains. Thus, our results, in opposition to a common view, suggest that the acquisition of plasmids does not significantly affect the bacteria fitness and, therefore, the theorized plasmid burden would not be a significant barrier for plasmid spread.

Antimicrobial resistance, β-lactamase genotypes, and plasmid replicon types of Shiga toxin-producing Escherichia coli isolated from different animal hosts

AIMS

The primary objective of this study was to analyze antimicrobial resistance (AMR), with a particular focus on β-lactamase genotypes and plasmid replicon types of Shiga toxin-producing Escherichia coli (STEC) strains originating from various animal hosts.

METHODS AND RESULTS

A total of 84 STEC strains were isolated from cattle (n = 32), sheep/goats (n = 26), pigeons (n = 20), and wild animals (n = 6) between 2010 and 2018 in various regions of Iran. The Kirby-Bauer susceptibility test and multiple polymerase chain reaction (PCR) panels were employed to elucidate the correlation between AMR and plasmid replicon types in STEC isolates. The predominant replicon types were IncFIC and IncFIB in cattle (46.8%), IncFIC in sheep/goats (46.1%), IncA/C in pigeons (90%), and IncP in wild animals (50%). STEC of serogroups O113, O26, and O111 harbored the IncFIB (100%), IncI1 (80%), and IncFIC + IncA/C (100%) plasmids, respectively. A remarkable AMR association was found between ciprofloxacin (100%), neomycin (68.7%), and tetracycline (61.7%) resistance with IncFIC; amoxicillin + clavulanic acid (88.8%) and tetracycline (61.7%) with IncA/C; ciprofloxacin (100%) with IncFIB; fosfomycin (85.7%) and sulfamethoxazole + trimethoprim (80%) with IncI1. IncI1 appeared in 83.3%, 50%, and 100% of the isolates harboring blaCTX-M, blaTEM, and blaOXA β-lactamase genes, respectively.

CONCLUSIONS

The emergence of O26/IncI1/blaCTX-M STEC in cattle farms poses a potential risk to public health.

Coordination of prophage and global regulator leads to high enterotoxin production in staphylococcal food poisoning-associated lineage

Staphylococcus species in food produce Staphylococcal enterotoxins (SEs) that cause Staphylococcal food poisoning (SFP). More than 20 SE types have been reported, among which Staphylococcal enterotoxin A (SEA) has been recognized as one of the most important SEs associated with SFP. However, the regulatory mechanisms underlying its production remain unclear. Previously, we identified a major SFP clone in Japan, CC81 subtype-1, which exhibits high SEA production. In this study, we attempted to identify the factors contributing to this phenomenon. Thus, we demonstrated that the attenuation of the activity of endogenous regulator, Staphylococcal accessory regulator S (SarS), and the lysogenization of a high SEA-producing phage contributed to this phenomenon in CC81 subtype-1. Furthermore, our results indicated that SarS could directly bind to the promoter upstream of the sea gene and suppress SEA expression; this low SarS repression activity was identified as one of the reasons for the high SEA production observed. Therefore, we revealed that both exogenous and endogenous factors may probably contribute to the high SEA production. Our results confirmed that SE production is a fundamental and critical factor in SFP and clarified the associated production mechanism while enhancing our understanding as to why a specific clone frequently causes SFP.

IMPORTANCE

The importance of this study lies in its unveiling of a molecular regulatory mechanism associated with the most important food poisoning toxin and the evolution of Staphylococcal food poisoning (SFP)-associated clone. SFP is primarily caused by Staphylococcus aureus, with Staphylococcal enterotoxin A (SEA) being commonly involved in many cases. Thus, SEA has been recognized as a major toxin type. However, despite almost a century since its discovery, the complete mechanism of SEA production is as yet unknown. In this study, we analyzed an SEA-producing SFP clone isolated in East Asia and discovered that this strain, besides acquiring the high SEA-producing phage, exhibits remarkably high SEA production due to the low activity of SarS, an intrinsic regulatory factor. This is the first report documenting the evolution of the SFP clone through the coordinated action of exogenous mobile genetic factors and endogenous regulators on this notorious toxin.

L-glutamine protects against enterohemorrhagic Escherichia coli infection by inhibiting bacterial virulence and enhancing host defense concurrently

IMPORTANCE

The type 3 secretion system (T3SS) was obtained in many Gram-negative bacterial pathogens, and it is crucial for their pathogenesis. Environmental signals were found to be involved in the expression regulation of T3SS, which was vital for successful bacterial infection in the host. Here, we discovered that L-glutamine (Gln), the most abundant amino acid in the human body, could repress enterohemorrhagic Escherichia coli (EHEC) T3SS expression via nitrogen metabolism and therefore had potential as an antivirulence agent. Our in vitro and in vivo evidence demonstrated that Gln could decline EHEC infection by attenuating bacterial virulence and enhancing host defense simultaneously. We repurpose Gln as a potential treatment for EHEC infection accordingly.

Detection of Cleaved Stx2a in the Blood of STEC-Infected Patients

Typical hemolytic uremic syndrome (HUS) is mainly caused by Shiga toxin-producing Escherichia coli (STEC) releasing Shiga toxin 2 (Stx2). Two different structures of this AB5 toxin have been described: uncleaved, with intact B and A chains, and cleaved, with intact B and a nicked A chain consisting of two fragments, A1 and A2, connected by a disulfide bond. Despite having the same toxic effect on sensitive cells, the two forms differ in their binding properties for circulating cells, serum components and complement factors, thus contributing to the pathogenesis of HUS differently. The outcome of STEC infections and the development of HUS could be influenced by the relative amounts of uncleaved or cleaved Stx2 circulating in patients' blood. Cleaved Stx2 was identified and quantified for the first time in four out of eight STEC-infected patients' sera by a method based on the inhibition of cell-free translation. Cleaved Stx2 was present in the sera of patients with toxins bound to neutrophils and in two out of three patients developing HUS, suggesting its involvement in HUS pathogenesis, although in association with other bacterial or host factors.

Comparative evaluation of antimicrobial activity of human granulysin, bovine and porcine NK-lysins against Shiga toxin-producing Escherichia coli O157:H7

Shiga toxin-producing Escherichia coli (STEC) O157:H7 (O157) is a foodborne pathogen causing human disease ranging from hemorrhagic colitis and hemolytic uremic syndrome to kidney failure, while remaining harmless to cattle, its primary reservoir. The severity of the human disease associated mainly with Shiga toxin production and a global emergence of antibiotic resistant STEC highlights the need for effective non-antibiotic, pre-harvest strategies to reduce O157 in cattle, the principal source of human infection. Towards this goal three synthetic antimicrobial peptides (AMPs): human granulysin (hGRNL), bovine NK-lysin (bNK2A), and porcine NK-lysin (pNKL), were tested in vitro against O157 isolates. As expected, circular dichroism spectroscopy findings were consistent with a predominantly α-helical conformation for all three AMPs in an environment mimicking bacterial outer surface or liposaccharides. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations of hGRNL (200 μM), bNK2A (12.5 μM against strain 86-24 and 25 μM against EDL933), and pNKL (6.25 μM) were determined using the Clinical and Laboratory Standards Institute broth microdilution method in Müeller-Hinton broth (cation-adjusted). The bNK2A and pNKL AMPs did not induce Shiga toxin expression in O157 at MIC, as there was a significant decrease or no change in toxin expression following 4- or 20 h incubation with the AMPs; bNK2A p <0.0001 (4 h) and p = 0.4831 (20 h); pNKL p <0.0001 (4 h) and p = 0.0001 (20 h). Propidium iodide uptake assay revealed faster O157 membrane damage or killing kinetics with bNK2A and pNKL compared to hGRNL. Nonetheless, transmission electron microscopy demonstrated that all three AMPs mediated damage to O157 membranes. In contrast, the three AMPs showed minimal cytotoxicity (<2%) against cattle red blood cells at tested concentrations (0.39-50 μM). Overall, our results demonstrate the potential for bNK2A and pNKL to be further developed into novel non-antibiotic agents to reduce O157 shedding in cattle.

Absence of Shiga toxin-producing Escherichia coli (STEC) in organic leafy greens from the metropolitan region of São Paulo, Brazil

Shiga toxin-producing Escherichia coli (STEC) is an important pathogen with public health implications, including its potential association with vegetables. In this study, we investigated the presence of STEC in vegetables obtained from organic producers located in São Paulo city, Brazil. As part of a routine surveillance study conducted over (years of isolation), a total of 200 samples of organic vegetables were screened using biochemical and PCR methods. Among the vegetable samples tested, 30 (15%) were positive for non-Shiga toxin-producing E. coli. While no STEC was detected in the organic vegetables in this study, the presence of non-STEC in vegetables raises concerns about the lack of proper hygiene practices during vegetable handling. This contamination represents a public health risk, particularly considering that these isolates can still be pathogenic, and vegetables are often consumed raw. To address this important issue, continuous monitoring of these farms is recommended to ensure the quality and safety of organic vegetables produced for both domestic consumption and exportation.

Comparison of Two Shiga Toxin-producing Escherichia coli (STEC) Isolation Protocols in Raw Cow's Milk Cheese Enrichment Broths: Direct STEC Isolation Versus Techniques Based on Immuno-concentration

The presence of Shiga toxin-producing Escherichia coli (STEC) in dairy products made with raw milk is a major concern for food safety authorities and industries. Two approaches have been proposed to isolate STEC from food. In the IC-Protocol (immuno-concentration protocol), specific serogroups are identified in the enrichment broth after the detection of the stx and eae genes. An immuno-concentration of the targeted serogroups is performed before isolating them on specific media. In the DI-Protocol (direct isolation protocol), a direct isolation of all STEC present in the enrichment broth is carried out after the detection of stx genes. We compared the ability of these two methods to isolate STEC O26:H11, O103:H2, O111:H8, O145:H28, and O157:H7 after artificial inoculation in four different raw milk cheeses. Across all serogroups and cheese types, STEC were isolated in 83.3% of samples when using the IC-Protocol but only 53.3% of samples with the DI-Protocol. For two cheese types, the DI-Protocol failed to isolate STEC O157:H7 strains altogether. Our results suggest that IC-Protocol is a robust methodology to effectively isolate STEC across a range of cheese types.

High-Throughput Microfluidic Quantitative PCR Platform for the Simultaneous Quantification of Pathogens, Fecal Indicator Bacteria, and Microbial Source Tracking Markers

Contamination of water with bacterial, viral, and protozoan pathogens can cause human diseases. Both humans and nonhumans can release these pathogens through their feces. To identify the sources of fecal contamination in the water environment, microbial source tracking (MST) approaches have been developed; however, the relationship between MST markers and pathogens is still not well understood most likely due to the lack of comprehensive datasets of pathogens and MST marker concentrations. In this study, we developed a novel microfluidic quantitative PCR (MFQPCR) platform for the simultaneous quantification of 37 previously validated MST markers, two fecal indicator bacteria (FIB), 22 bacterial, 11 viral, and five protozoan pathogens, and three internal amplification/process controls in many samples. The MFQPCR chip was applied to analyze pathogen removal rates during the wastewater treatment processes. In addition, multiple host-specific MST markers, FIB, and pathogens were successfully quantified in human and avian-impacted surface waters. While the genes for pathogens were relatively infrequently detected, positive correlations were observed between some potential pathogens such as Clostridium perfringens and Mycobacterium spp., and human MST markers. The MFQPCR chips developed in this study, therefore, can provide useful information to monitor and improve water quality.

Predictive Population Dynamics of Escherichia coli O157:H7 and Salmonella enterica on Plants: a Mechanistic Mathematical Model Based on Weather Parameters and Bacterial State

Weather affects key aspects of bacterial behavior on plants but has not been extensively investigated as a tool to assess risk of crop contamination with human foodborne pathogens. A novel mechanistic model informed by weather factors and bacterial state was developed to predict population dynamics on leafy vegetables and tested against published data tracking Escherichia coli O157:H7 (EcO157) and Salmonella enterica populations on lettuce and cilantro plants. The model utilizes temperature, radiation, and dew point depression to characterize pathogen growth and decay rates. Additionally, the model incorporates the population level effect of bacterial physiological state dynamics in the phyllosphere in terms of the duration and frequency of specific weather parameters. The model accurately predicted EcO157 and S. enterica population sizes on lettuce and cilantro leaves in the laboratory under various conditions of temperature, relative humidity, light intensity, and cycles of leaf wetness and dryness. Importantly, the model successfully predicted EcO157 population dynamics on 4-week-old romaine lettuce plants under variable weather conditions in nearly all field trials. Prediction of initial EcO157 population decay rates after inoculation of 6-week-old romaine plants in the same field study was better than that of long-term survival. This suggests that future augmentation of the model should consider plant age and species morphology by including additional physical parameters. Our results highlight the potential of a comprehensive weather-based model in predicting contamination risk in the field. Such a modeling approach would additionally be valuable for timing field sampling in quality control to ensure the microbial safety of produce. IMPORTANCE Fruits and vegetables are important sources of foodborne disease. Novel approaches to improve the microbial safety of produce are greatly lacking. Given that bacterial behavior on plant surfaces is highly dependent on weather factors, risk assessment informed by meteorological data may be an effective tool to integrate into strategies to prevent crop contamination. A mathematical model was developed to predict the population trends of pathogenic E. coli and S. enterica, two major causal agents of foodborne disease associated with produce, on leaves. Our model is based on weather parameters and rates of switching between the active (growing) and inactive (nongrowing) bacterial state resulting from prevailing environmental conditions on leaf surfaces. We demonstrate that the model has the ability to accurately predict dynamics of enteric pathogens on leaves and, notably, sizes of populations of pathogenic E. coli over time after inoculation onto the leaves of young lettuce plants in the field.

Assessment of interleukin-10 promoter variant (-1082A/G) and cytokine production in patients with hemolytic uremic syndrome

Introduction

Hemolytic uremic syndrome (HUS) is a condition that results in acute kidney failure mainly in children, which is caused by Shiga toxin-producing Escherichia coli and inflammatory response. Although anti-inflammatory mechanisms are triggered, studies on the implication in HUS are scarce. Interleukin-10 (IL-10) regulates inflammation in vivo, and the interindividual differences in its expression are related to genetic variants. Notably, the single nucleotide polymorphism (SNP) rs1800896 -1082 (A/G), located in the IL-10 promoter, regulates cytokine expression.

Methods

Plasma and peripheral blood mononuclear cells (PBMC) were collected from healthy children and HUS patients exhibiting hemolytic anemia, thrombocytopenia, and kidney damage. Monocytes identified as CD14⁺ cells were analyzed within PBMC by flow cytometry. IL-10 levels were quantified by ELISA, and SNP -1082 (A/G) was analyzed by allele-specific PCR.

Results

Circulating IL-10 levels were increased in HUS patients, but PBMC from these patients exhibited a lower capacity to secrete this cytokine compared with those from healthy children. Interestingly, there was a negative association between the circulating levels of IL-10 and inflammatory cytokine IL-8. We observed that circulating IL-10 levels were threefold higher in HUS patients with -1082G allele in comparison to AA genotype. Moreover, there was relative enrichment of GG/AG genotypes in HUS patients with severe kidney failure.

Discussion

Our results suggest a possible contribution of SNP -1082 (A/G) to the severity of kidney failure in HUS patients that should be further evaluated in a larger cohort.

Detecting Enteric Pathogens in Low-Risk Drinking Water in Dhaka, Bangladesh: An Assessment of the WHO Water Safety Categories

The microbiological quality of water is usually assessed by fecal coliform bacteria, and the presence of E. coli as an indicator of fecal contamination is widely recommended by international guidelines. This study aimed to assess the prevalence of diarrheagenic pathogens, in both public and personal domain water sources and examine the reliance on the WHO drinking water risk assessment guidelines. This study was conducted in a low-income urban community in Dhaka, Bangladesh between September 2014 and October 2015. Polymerase chain reaction (PCR) was used to detect the marker and virulence genes of Escherichia coli, Vibrio cholerae, Salmonella species, and Campylobacter species, and the culture method was employed for the quantitative assessment of E. coli. According to the WHO guidelines, 48% of the public domain source water and 21% of the personal domain point-of-drinking water were classified in the low-risk group, i.e., 0 CFU of E. coli/100 mL. However, when using PCR, we detected pathogens in 39% (14/36) of the point-of-drinking water samples and 65% (74/114) of the public domain water source samples classified in the low-risk group. Our study showed that relying solely on E. coli detection as a measure of water quality may overlook the presence of other pathogens in the drinking water. In addition to the culture-based method, the detection of virulence genes by PCR should also be considered to add more scrutiny to the detection of diverse types of pathogens.

EFFECTS OF BACTERIAL LIPOPOLYSACCHARIDE AND SHIGA TOXIN ON INDUCED PLURIPOTENT STEM CELL-DERIVED MESENCHYMAL STEM CELLS

ABSTRACT

Background : Mesenchymal stem cells (MSCs) can be activated by different bacterial toxins. Lipopolysaccharides and Shiga Toxin (Stx) are the main toxins necessary for hemolytic uremic syndrome development. The main etiological event in this disease is endothelial damage that causes glomerular destruction. Considering the repairing properties of MSC, we aimed to study the response of MSC derived from induced pluripotent stem cells (iPSC-MSC) to LPS and/or Stx and its effect on the restoration of injured endothelial cells. Methods : iPSC-MSC were treated with LPS and or/Stx for 24 h and secretion of cytokines, adhesion, and migration were measured in response to these toxins. In addition, conditioned media from treated iPSC-MSC were collected and used for proteomics analysis and evaluation of endothelial cell healing and tubulogenesis using human microvascular endothelial cells 1 as a source of endothelial cells. Results : The results obtained showed that LPS induced a proinflammatory profile on iPSC-MSC, whereas Stx effects were less evident, even though cells expressed the Gb 3 receptor. Moreover, LPS induced on iPSC-MSC an increment in migration and adhesion to a gelatin substrate. Addition of conditioned media of iPSC-MSC treated with LPS + Stx, decreased the capacity of human microvascular endothelial cells 1 to close a wound, and did not favor tubulogenesis. Proteomic analysis of iPSC-MSC treated with LPS and/or Stx revealed specific protein secretion patterns that support the functional results described. Conclusions : iPSC-MSC activated by LPS acquired a proinflammatory profile that induces migration and adhesion to extracellular matrix proteins but the addition of Stx did not activate any repair program to ameliorate endothelial damage, indicating that the use of iPSC-MSC to regenerate endothelial injury caused by LPS and/or Stx in hemolytic uremic syndrome could not be the best option to consider to regenerate a tissue injury.

Determination of biological activities of nanoparticles containing silver and copper in water disinfection with/without ultrasound technique

The final and most crucial step in obtaining clean water is disinfection. More innovative methods of water disinfection have recently been sought. Water disinfection is a promising application for nanoparticles as disinfectants. As a contribution to the literature, biofilm and metal-containing nanoparticles as antiadhesion inhibitors were used in conjunction with ultrasound in this study. The microbroth dilution test was used to reveal the microbiological antibacterial activities of different concentrations of AgNO3 and CuCl2 containing nanoparticles against the Escherichia coli ATCC 25,922 strain, which is an indicator bacterium in water systems. Antibiofilm activities were then investigated using biofilm attachment and biofilm inhibition tests. The inhibitory effect of nanoparticle ultrasonic waves on biofilm contamination was determined using a novel approach. Human keratinocyte cells (HaCaT cell line) were used in cell culture studies after water disinfection, and their cytotoxic effects were demonstrated using the MTT assay. The findings suggest that the nanoparticles utilized might be a viable choice for water disinfection applications. Furthermore, employing ultrasound at low doses with nanoparticles resulted in greater results. One feasible option is to employ nanoparticles to cleanse water without producing cytotoxicity.

Antibacterial effect of kitchen herbs against pathogenic multidrug-resistant E. coli isolates from calf diarrhoea

Calf diarrhoea remains the biggest challenge both in the small and large farms. Infectious diarrhoea is associated with many pathogens, Escherichia coli being one, but majority are systematically treated with antibiotics. Since antimicrobial resistance (AMR) is a growing menace, the need to find alternative prophylactic solutions using popular kitchen herbs such as Trachyspermum ammi (carom seeds), Curcuma longa (turmeric) and cinnamon (Cinnamomum sp.) extracts is been investigated against virulent form of E. coli isolated from calf diarrhoea. The virulence factors identified in these isolates were ST (32.5%), LT (20%), eaeA (15%), stx1 (2.5%) and stx2 (5%) with the occurrence of the most common serogroups as O18 (15%) followed by O111 (12.5%). Highest resistance was seen with beta lactam + beta lactamase inhibitor (amoxicillin/clavulanic acid) followed by beta lactams (ampicillin, cefuroxime and cefepime). The zone of inhibition due to cinnamon (methanol) and carom seed (ethanol) extracts (500 to 250 μg/mL concentration) on E. coli bacteria was >19 mm, respectively. Turmeric, cinnamon and carom had the potency of inhibiting the pathogenic E. coli which maybe suggestive of its use in calf diets as prophylaxis against diarrhoea.

Molecular serotyping of Shiga toxin-producing Escherichia coli (STEC) of animal origin in Iran reveals the presence of important non-O157 seropathotypes

The present study reported the first serotyping (O:H typing) data documented in Shiga toxin-producing Escherichia coli (STEC) strains of animal origin in Iran in isolates recovered between 2008 to 2016. A total number of 75 STEC strains previously isolated from fecal samples of cattle, sheep, goats, pigeons, humans, and deer were assessed by different polymerase chain reaction (PCR) assays detecting the major virulence genes of STEC and phylogroups. Then, the strains were tested for the 16 important O-groups by PCR. Finally, twenty strains were selected for H-genotyping by PCR plus sequencing. The predominant serogroup was O113 which was detected in nine isolates (five cattle, 55.50%; two goats, 22.20%; two red deer, 22.20%) followed by O26 (3/3, 100%) in cattle, O111 (3/3, 100%) in cattle, O5 (3/3, 100%) in sheep, O63 (1/1, 100%) in pigeon, O75 (2/2, 100%) in pigeons, and O128 in goats (2/3, 66.60%) and pigeon (1/3, 33.30%). The most important recognized serotypes were O113:H21 in cattle (2/3) and goat (1/3), O113:H4 in red deer (1/1), O111:H8 in calves (2/2), O26:H11 in calve (1/1), O128:H2 in goats (2/3) and pigeon (1/3), and O5:H19 in sheep (3/3). One cattle strain carrying stx1, stx2, eae, and Ehly genes belonged to O26:H29 serotype. Most strains with determined O-groups were from the bovine source that highlighted the importance of cattle as reservoirs of potentially pathogenic serovars. The present study suggested that the top seven non-O157 serogroups should be assessed along with O157 in all future research and clinical diagnostics of STEC in Iran.

Occurrence and genetic characterization of Shiga toxin-producing Escherichia coli on bovine and pork carcasses and the environment from transport trucks

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens causing severe diseases. The ability of STEC to produce disease is associated with Shiga toxin (Stx) production. We investigated the occurrence of STEC on bovine and pork carcasses and walls of trucks where they were transported, and we characterized virulence genes and serotypes of STEC strains. We compared the whole genomic sequencing of a STEC O157:H7 strain isolated from a bovine carcass in this work and a STEC O157:H7 strain isolated from a child with HUS, both isolated in 2019. We studied the relationship between these isolates and others collected in the database. The results show a 40% of STEC and two different serogroups were identified (O130 and O157). STEC O157:H7 were isolated from bovine carcasses and harbored stx2, eae, ehxA, katP, espP, stcE, ECSP_0242/1773/2687/2870/2872/3286/3620 and were classified as lineage I/II. In STEC non-O157 isolates, three isolates were isolated from bovine carcasses and harbored the serogroup O130 and one strain isolated from pork carcasses was O-non-typeable. All STEC non-O157 harbored sxt1 gene. The analysis from the whole genome showed that both STEC O157:H7 strains belonged to the hypervirulent clade 8, ST11, phylogroup E, carried the allele tir 255 T > A T, and they were not clonal. The analysis of information allows us to conclude that the STEC strains circulate in pork and bovine carcasses arriving in transport. This situation represents a risk for the consumers and the need to implement an integrated STEC control in the food chain.

Mechanism for inhibition of cytotoxicity of Shiga toxin by luteolin

Enterohemorrhagic or Shiga toxin-producing Escherichia coli is a food-poisoning bacterium that grows in the intestine to produce Shiga toxin (Stx). In this study, the effects of 20 polyphenols on the cytotoxicity of Stx1 and Stx2 in Vero cells were investigated. Among these, epigallocatechin gallate, butein, isorhapontigenin, hesperetin, morin, luteolin, resveratrol, and rhapontigenin showed inhibitory effects on the cytotoxicity of Stxs at 0.4 mmol/L. Furthermore, Vero cells pre-treated with these polyphenols were resistant to Stx at 0.4 mmol/L. However, luteolin showed the most potent inhibitory and cytoprotective effect against Stxs at 0.08 mmol/L or more. This inhibitory mechanism of luteolin was determined using a cell-free protein synthesis system and quantitative reverse transcription PCR assay to detect depurination of 28S rRNA in Vero cells. Luteolin did not inhibit the cell-free protein synthesis by Stxs, suggesting that the enzymatic activity of the Stx A subunit was not inhibited by luteolin. The depurination of 28S rRNA by Stxs was also investigated in Vero cells. The 28S rRNA depurination by Stxs was suppressed in Vero cells treated with Stxs which had been pretreated with luteolin. These results suggest that luteolin inhibits the incorporation of Stxs into Vero cells. This is the first report to show that luteolin inhibits the cytotoxicity of both Stx1 and Stx2 by inhibiting the incorporation of Stxs into Vero cells.

Tail-Engineered Phage P2 Enables Delivery of Antimicrobials into Multiple Gut Pathogens

Bacteriophages can be reprogrammed to deliver antimicrobials for therapeutic and biocontrol purposes and are a promising alternative treatment to antimicrobial-resistant bacteria. Here, we developed a bacteriophage P4 cosmid system for the delivery of a Cas9 antimicrobial into clinically relevant human gut pathogens Shigella flexneri and Escherichia coli O157:H7. Our P4 cosmid design produces a high titer of cosmid-transducing units without contamination by a helper phage. Further, we demonstrate that genetic engineering of the phage tail fiber improves the transduction efficiency of cosmid DNA in S. flexneri M90T as well as allows recognition of a nonnative host, E. coli O157:H7. We show that the transducing units with the chimeric tails enhanced the overall Cas9-mediated killing of both pathogens. This study demonstrates the potential of our P4 cas9 cosmid system as a DNA sequence-specific antimicrobial against clinically relevant gut pathogenic bacteria.

Prevalence, virulence factors, and antimicrobial resistance profiles of Shiga toxin-producing Escherichia coli isolated from broiler chickens in Egypt

Pathogenic Escherichia coli is one of the world's most important zoonotic foodborne pathogens and poses a serious threat to public health. We examined the prevalence, virulence genes, and antibiotic resistance profile of Shiga toxin (Stx)-producing E. coli (STEC) isolated from broiler chickens in the Kafr El-Sheikh governorate, Egypt. A total of 410 samples (230 cloacal swabs, 180 internal organs) were collected to isolate E. coli. A total of 29 (7.07%) E. coli isolates were recovered and identified, and 18 of them harbored Stx genes (stx). Out of 18 isolates, five (17.24%) carried the stx 1 gene, five (17.24%) carried the stx 2 gene, four (13.79%) carried both stx 1 and stx 2 genes, and four (13.79%) carried stx 1 , stx 2 , and eae A genes. Overall, complete anti-biotic resistance was observed against amoxicillin, ampicillin, cefpodoxime, and cefoperazone; high resistance was observed against ampicillin/sulbactam, nalidixic acid, cefuroxime, aztreonam, ciprofloxacin, ceftriaxone, chloramphenicol, sulfamethoxazole/trimethoprim, and ceftazidime; moderate resistance against gentamicin; low resistance against cefoxitin; lower resistance was detected against norfloxacin, cefotetan, and amikacin; and the lowest resistance against imipenem. All E. coli isolates demonstrated multidrug resistance against at least four antibiotic classes. Out of 29 E. coli isolates, STEC accounted for 18 isolates, of which the O78, O26:H11, O128:H2, O1:H7, O119:H6, and O91:H21 serogroups were predominant. All E. coli isolates were multidrug resistant and therefore pose a potential public health concern as these virulent, resistant strains may spread to humans. Thus, high levels of hygiene and biosecurity are required by chicken handlers to decrease the danger of infection spreading to humans.

Development of a novel tetravalent peptide that absorbs subtilase cytotoxin by targeting the receptor-binding B-subunit

Subtilase cytotoxin (SubAB) is a major virulence factor produced by eae-negative Shiga-toxigenic Escherichia coli (STEC) that can cause fatal systemic complications. SubAB binds to target cells through multivalent interactions between its B-subunit pentamer and receptor molecules such as glycoproteins with a terminal N-glycolylneuraminic acid (Neu5Gc). We screened randomized multivalent peptide libraries synthesized on a cellulose membrane and identified a series of tetravalent peptides that efficiently bind to the receptor-binding region of the SubAB B-subunit pentamer. These peptides competitively inhibited the binding of the B-subunit to a receptor-mimic molecule containing clustered Neu5Gc (Neu5Gc-polymer). We selected the peptide with the highest inhibitory efficacy, FFP-tet, and covalently bound it to beads to synthesize FFP-tet-beads, a highly clustered SubAB absorber that displayed potency to absorb SubAB cytotoxicity through direct binding to the toxin. The efficacy of FFP-tet-beads to absorb SubAB cytotoxicity in solution was similar to that of Neu5Gc-polymer, suggesting that FFP-tet-beads might be an effective therapeutic agent against complications arising from eae-negative STEC infection.

Prevalence and Implications of Shiga Toxin-Producing E. coli in Farm and Wild Ruminants

Shiga-toxin-producing Escherichia coli (STEC) is a food-borne pathogen that causes human gastrointestinal infections across the globe, leading to kidney failure or even death in severe cases. E. coli are commensal members of humans and animals' (cattle, bison, and pigs) guts, however, may acquire Shiga-toxin-encoded phages. This acquisition or colonization by STEC may lead to dysbiosis in the intestinal microbial community of the host. Wildlife and livestock animals can be asymptomatically colonized by STEC, leading to pathogen shedding and transmission. Furthermore, there has been a steady uptick in new STEC variants representing various serotypes. These, along with hybrids of other pathogenic E. coli (UPEC and ExPEC), are of serious concern, especially when they possess enhanced antimicrobial resistance, biofilm formation, etc. Recent studies have reported these in the livestock and food industry with minimal focus on wildlife. Disturbed natural habitats and changing climates are increasingly creating wildlife reservoirs of these pathogens, leading to a rise in zoonotic infections. Therefore, this review comprehensively surveyed studies on STEC prevalence in livestock and wildlife hosts. We further present important microbial and environmental factors contributing to STEC spread as well as infections. Finally, we delve into potential strategies for limiting STEC shedding and transmission.

Weather stressors correlate with Escherichia coli and Salmonella enterica persister formation rates in the phyllosphere: a mathematical modeling study

Enteric pathogens can enter a persister state in which they survive exposure to antibiotics and physicochemical stresses. Subpopulations of such phenotypic dormant variants have been detected in vivo and in planta in the laboratory, but their formation in the natural environment remains largely unexplored. We applied a mathematical model predicting the switch rate to persister cell in the phyllosphere to identify weather-related stressors associated with E. coli and S. enterica persister formation on plants based on their population dynamics in published field studies from the USA and Spain. Model outputs accurately depicted the bi-phasic decay of bacterial population sizes measured in the lettuce and spinach phyllosphere in these studies. Predicted E. coli persister switch rate on leaves was positively and negatively correlated with solar radiation intensity and wind velocity, respectively. Likewise, predicted S. enterica persister switch rate correlated positively with solar radiation intensity; however, a negative correlation was observed with air temperature, relative humidity, and dew point, factors involved in water deposition onto the phylloplane. These findings suggest that specific environmental factors may enrich for dormant bacterial cells on plants. Our model quantifiably links persister cell subpopulations in the plant habitat with broader physical conditions, spanning processes at different granular scales.

Molecular Characterization of Shiga Toxin Produced by Escherichia coli Isolated from Milk Samples in Baghdad City

Raw milk is a nutrient-rich food that is considered a high-quality nutritional medium for many microorganism, including Escherichia coli. The aim of the present work was the diagnosis, by molecular methods, of Shiga toxins produced by E. coli strains isolated from cow milk samples collected from different farms in Al-Mahmmodia, Al yoosifya, Al lattiffya, Al howasha, and Arab Jboor in the government of Baghdad during the summer season. Milk samples were incubated in media for bacterial isolation. Isolates were identified using Gram staining and biochemical tests. Out of 50 samples, 15 (30%) showed the presence of E. coli. To confirm the identity of the isolates, their 16S rRNA genes were amplified using specific primers. The results showed that all isolates were E. coli. Shiga toxin-producing E. coli (STEC) were detected among the samples. The prevalence of stx1 genes was higher than that of stx2 among them. No STECs were found among six of the sample isolates, and none of these isolates was positive for stx1 and stx2. SDS-PAGE was used to determine the molecular weight of the toxin, and four selected E. coli bacteria producing Shiga-like toxins showed a clear band of approximately 70 kDa.

SARS-CoV-2 and Emerging Foodborne Pathogens: Intriguing Commonalities and Obvious Differences

The coronavirus disease 2019 (COVID-19) has resulted in tremendous human and economic losses around the globe. The pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a virus that is closely related to SARS-CoV and other human and animal coronaviruses. Although foodborne diseases are rarely of pandemic proportions, some of the causative agents emerge in a manner remarkably similar to what was observed recently with SARS-CoV-2. For example, Shiga toxin-producing Escherichia coli (STEC), the most common cause of hemolytic uremic syndrome, shares evolution, pathogenesis, and immune evasion similarities with SARS-CoV-2. Both agents evolved over time in animal hosts, and during infection, they bind to specific receptors on the host cell's membrane and develop host adaptation mechanisms. Mechanisms such as point mutations and gene loss/genetic acquisition are the main driving forces for the evolution of SARS-CoV-2 and STEC. Both pathogens affect multiple body organs, and the resulting diseases are not completely cured with non-vaccine therapeutics. However, SARS-CoV-2 and STEC obviously differ in the nature of the infectious agent (i.e., virus vs. bacterium), disease epidemiological details (e.g., transmission vehicle and symptoms onset time), and disease severity. SARS-CoV-2 triggered a global pandemic while STEC led to limited, but sometimes serious, disease outbreaks. The current review compares several key aspects of these two pathogenic agents, including the underlying mechanisms of emergence, the driving forces for evolution, pathogenic mechanisms, and the host immune responses. We ask what can be learned from the emergence of both infectious agents in order to alleviate future outbreaks or pandemics.

Virulence, antimicrobial susceptibility, and phylogenetic analysis of Cronobacter sakazakii isolates of food origins from Jordan

AIMS

to characterize a collection of Cronobacter sakazakii isolates collected from various origins in Jordan.

METHODS AND RESULTS

the isolates were characterized using 16S rRNA sequencing, DNA microarray, multi-locus sequence typing (MLST), O-serotyping, virulence gene identification, and antibiotic susceptibility testing. The identities and phylogenetic relatedness revealed that C. sakazakii sequence type 4 (ST4) and Csak O:1 serotype was the most prevalent STs and serovars among these C. sakazakii strains. PCR screening of putative virulence genes showed that the siderophore-interacting protein gene (sip) and iron acquisition gene clusters (eitCBAD and iucABCD/iutA) were the most detected genes with noticeable variability in the type 6 secretion system (T6SS) and filamentous hemagglutinin/adhesion (FHA) gene loci. The antibiotic resistance profiles revealed that the majority of the isolates were susceptible to all antibiotics used despite harboring a class C β-lactamase resistance gene.

CONCLUSIONS

the results described in this report provide additional insights about the considerable genotypic and phenotypic heterogeneity within C. sakazakii.

SIGNIFICANCE AND IMPACT OF THE STUDY

the information reported in this study might be of great value in understanding the origins of C. sakazakii isolates, in addition to their diversity and variability, which might be helpful in preventing future outbreaks of this pathogen.

Cinnamomum: The New Therapeutic Agents for Inhibition of Bacterial and Fungal Biofilm-Associated Infection

Due to the potent antibacterial properties of Cinnamomum and its derivatives, particularly cinnamaldehyde, recent studies have used these compounds to inhibit the growth of the most prevalent bacterial and fungal biofilms. By inhibiting flagella protein synthesis and swarming motility, Cinnamomum could suppress bacterial attachment, colonization, and biofilm formation in an early stage. Furthermore, by downregulation of Cyclic di‐guanosine monophosphate (c‐di‐GMP), biofilm-related genes, and quorum sensing, this compound suppresses intercellular adherence and accumulation of bacterial cells in biofilm and inhibits important bacterial virulence factors. In addition, Cinnamomum could lead to preformed biofilm elimination by enhancing membrane permeability and the disruption of membrane integrity. Moreover, this substance suppresses the Candida species adherence to the oral epithelial cells, leading to the cell wall deformities, damage, and leakages of intracellular material that may contribute to the established Candida’s biofilm elimination. Therefore, by inhibiting biofilm maturation and destroying the external structure of biofilm, Cinnamomum could boost antibiotic treatment success in combination therapy. However, Cinnamomum has several disadvantages, such as poor solubility in aqueous solution, instability, and volatility; thus, the use of different drug-delivery systems may resolve these limitations and should be further considered in future investigations. Overall, Cinnamomum could be a promising agent for inhibiting microbial biofilm-associated infection and could be used as a catheter and other medical materials surface coatings to suppress biofilm formation. Nonetheless, further in vitro toxicology analysis and animal experiments are required to confirm the reported molecular antibiofilm effect of Cinnamomum and its derivative components against microbial biofilm.

A unique peptide-based pharmacophore identifies an inhibitory compound against the A-subunit of Shiga toxin

Shiga toxin (Stx), a major virulence factor of enterohemorrhagic Escherichia coli (EHEC), can cause fatal systemic complications. Recently, we identified a potent inhibitory peptide that binds to the catalytic A-subunit of Stx. Here, using biochemical structural analysis and X-ray crystallography, we determined a minimal essential peptide motif that occupies the catalytic cavity and is required for binding to the A-subunit of Stx2a, a highly virulent Stx subtype. Molecular dynamics simulations also identified the same motif and allowed determination of a unique pharmacophore for A-subunit binding. Notably, a series of synthetic peptides containing the motif efficiently inhibit Stx2a. In addition, pharmacophore screening and subsequent docking simulations ultimately identified nine Stx2a-interacting molecules out of a chemical compound database consisting of over 7,400,000 molecules. Critically, one of these molecules markedly inhibits Stx2a both in vitro and in vivo, clearly demonstrating the significance of the pharmacophore for identifying therapeutic agents against EHEC infection.

Presence of Escherichia coli O157:H7 in Dairy Farms located in Najaf, Baghdad, Kirkuk, and Erbil, Iraq

It has been approved that one of the most dangerous foodborne pathogenic bacteria is E. coli O157:H7, which is responsible for several infection and death cases worldwide. It is well documented that in the developing countries E. coli O157:H7 is considered the main causative pathogen of human gastrointestinal infections. Therefore, the current research was aimed to evaluate the prevalence of E. coli O157:H7 in dairy cattle's milk using a rapid method, in Iraq (Najaf, Baghdad, Kirkuk, and Erbil). Over a period of 6 months (During hot months) samples were obtained and investigated by culturing on selective media (CT-SMAC). The multiplex PCR (m-PCR) also used for milk sample direct investigation. Using biochemical tests the recorded data showed that, 2 recognized isolates were E. coli, while the recorded data obtained from m-PCR assay revealed that none of the isolated E. coli was toxigenic E.coli O157:H7. The results of m-PCR on the milk samples revealed that 45 milk samples contained at least one of the following genes: O157, H7, stx1, stx2 genes. Also the results of the m-PCR revealed that 2 samples (raw milk) were toxigenic O157:H7 positive. In conclusion, to the best of authors' knowledge, this investigation was the first report on the prevalence of E. coli O157:H7 in the raw milk samples in Iraq. The results showed that the proportion of contaminated milk samples contaminated with E. coli O157:H7 identified in the current survey were similar to that the results of the previously published research from different dairy products across different countries in the Middle East region.

Neutrophil Extracellular Traps Induced by Shiga Toxin and Lipopolysaccharide-Treated Platelets Exacerbate Endothelial Cell Damage

Hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in the pediatric population. The etiology of HUS is linked to Gram-negative, Shiga toxin (Stx)-producing enterohemorrhagic bacterial infections. While the effect of Stx is focused on endothelial damage of renal glomerulus, cytokines induced by Stx or bacterial lipopolysaccharide (LPS) and polymorphonuclear cells (PMNs) are involved in the development of the disease. PMN release neutrophil extracellular traps (NETs) to eliminate pathogens, although NETs favor platelets (Plts) adhesion/thrombus formation and can cause tissue damage within blood vessels. Since thrombus formation and occlusion of vessels are characteristic of HUS, PMN–Plts interaction in the context of Stx may promote netosis and contribute to the endothelial damage observed in HUS. The aim of this study was to determine the relevance of netosis induced by Stx in the context of LPS-sensitized Plts on endothelial damage. We observed that Stx2 induced a marked enhancement of netosis promoted by Plts after LPS stimulation. Several factors seemed to promote this phenomenon. Stx2 itself increased the expression of its receptor on Plts, increasing toxin binding. Stx2 also increased LPS binding to Plts. Moreover, Stx2 amplified LPS induced P-selectin expression on Plts and mixed PMN–Plts aggregates formation, which led to activation of PMN enhancing dramatically NETs formation. Finally, experiments revealed that endothelial cell damage mediated by PMN in the context of Plts treated with LPS and Stx2 was decreased when NETs were disrupted or when mixed aggregate formation was impeded using an anti-P-selectin antibody. Using a murine model of HUS, systemic endothelial damage/dysfunction was decreased when NETs were disrupted, or when Plts were depleted, indicating that the promotion of netosis by Plts in the context of LPS and Stx2 plays a fundamental role in endothelial toxicity. These results provide insights for the first time into the pivotal role of Plts as enhancers of endothelial damage through NETs promotion in the context of Stx and LPS. Consequently, therapies designed to reduce either the formation of PMN–Plts aggregates or NETs formation could lessen the consequences of endothelial damage in HUS.

Prevalence and Molecular Characterisation of Extended-Spectrum Beta-Lactamase-Producing Shiga Toxin-Producing Escherichia coli, from Cattle Farm to Aquatic Environments

Extended-spectrum beta-lactamase (ESBL)-producing bacteria are a major problem for public health worldwide because of limited treatment options. Currently, only limited information is available on ESBL-producing Shiga toxin-producing Escherichia coli (STEC) in cattle farms and the surrounding aquatic environment. This study sought to track and characterise ESBL-producing STEC disseminating from a cattle farm into the water environment. Animal husbandry soil (HS), animal manure (AM), animal drinking water (ADW), and nearby river water (NRW) samples were collected from the cattle farm. Presumptive ESBL-producing STEC were isolated and identified using chromogenic media and mass spectrophotometry methods (MALDI-TOF-MS), respectively. The isolates were subjected to molecular analysis, and all confirmed ESBL-producing STEC isolates were serotyped for their O serogroups and assessed for antibiotic resistance genes (ARGs) and for the presence of selected virulence factors (VFs). A phylogenetic tree based on the multilocus sequences was constructed to determine the relatedness among isolates of ESBL-producing STEC. The highest prevalence of ESBL-producing STEC of 83.33% was observed in HS, followed by ADW with 75%, NRW with 68.75%, and the lowest was observed in AM with 64.58%. Out of 40 randomly selected isolates, 88% (n = 35) belonged to the serogroup O45 and 13% (n = 5) to the serogroup O145. The multilocus sequence typing (MLST) analysis revealed four different sequence types (STs), namely ST10, ST23, ST165, and ST117, and the predominant ST was found to be ST10. All 40 isolates carried sul1 (100%), while bla_OXA, bla_CTX-M, sul2, bla_TEM, and qnrS genes were found in 98%, 93%, 90%, 83%, and 23% of the 40 isolates, respectively. For VFs, only stx2 was detected in ESBL-producing STEC isolates. The results of the present study indicated that a cattle environment is a potential reservoir of ESBL-producing STEC, which may disseminate into the aquatic environment through agricultural runoff, thus polluting water sources. Therefore, continual surveillance of ESBL-producing STEC non-O157 would be beneficial for controlling and preventing STEC-related illnesses originating from livestock environments.

Prevalence of Shiga toxin-producing Escherichia coli and Salmonellae and some associated hematologic and biochemical profile alterations in lambs

Lamb enteritis constitutes an economic burden on sheep production worldwide. We aimed to estimate the prevalence of Shiga toxin-producing Escherichia coli (STEC) and Salmonellae among diarrheic lambs at Kafrelsheikh Governorate, Egypt and to detect the associated clinical, hematologic, biochemical, and antioxidant parameters. Fifty diarrheic and twenty apparently healthy control lambs were examined clinically, and hematologically. Diarrheic lambs had a significant elevated body temperature, respiratory and pulse rate, most of hemogram para-meters, total proteins and albumin, oxidative stress markers malonaldiahyde and nitric oxide levels, liver enzymes, urea and creatinine than control group. On the other hand, these diarrheic lambs had significant reduction in total leukocyte count and lymphocytes, antioxidant biomarkers super oxide dismutase activities and reduced glutathione than control lambs. E. coli and Salmonella spp. were isolated from 32.00% and 16.00% of diseased lambs, respectively. Serotyping and biochemical tests of examined samples identified 16 E. coli isolates belonged to 10 different serotypes; O6, O8, O26:H11, O75, O84:H21, O103:H2, O114:H4, O121:H7, O128:H2 and O163:H2. All isolates are STEC as they harbor either Shiga-toxin 1 or Shiga-toxin 2 genes or both. One isolate carries intimin gene (eaeA) and classified as EHEC; O26:H11. The obtained nine isolates of Salmonella carry enterotoxin (Stn) genes, eight of them carry hyper-invasive locus (hilA) gene, all isolates belonged to six serotypes; S. Enteritidis, S. Heidelberg, S. Tsevie, S. Typhimurium, S. Essen, and S. Infantis. Lamb diarrhea was prevalent in the studied area and might constitute a veterinary and public health threat. Alteration in hemato-biochemical para-meters and oxidative-anti-oxidant balance could help adopt appropriate treatment regimens.

Occurrence of multiple drug-resistant Shiga toxigenic Escherichia coli in raw milk samples collected from retail outlets in South India

The prevalence of Shiga-toxigenic E. coli (STEC), harbouring multidrug-resistant genes in raw milk collected from household vendors and cooperative milk marketing societies in Ernakulam District, Kerala, India, has been investigated. A higher prevalence of STEC pathotypes, with 47.16% (20 out of 42 samples), was observed in raw milk. A total of 157 STEC isolates were identified, which included notorious pathoserotypes, E. coli O157 group (10.19%) and E. coli non-O157 group 5.73%). All of the tested STEC isolates were multidrug-resistant and showed resistance to at least six different antibiotics. Two of the isolates showed resistance to 14 different antibiotics tested. Cent percentage resistance was observed for Penicillin, Cefalexine, Rifampicin, Methicillin, and Novobiocin. We observed in phenotypic assays that 26.75% of STEC isolates are ESBL producers. The bla TEM gene, a characteristic marker for ESBL production, was detected in 42.85% of the isolates. The study points out the risk of virulent and multidrug-resistant STEC in raw milk and the need for stringent quality surveillance and assurance plans to alleviate the potential public health threat.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-021-05226-x.

Novel reusable animal model for comparative evaluation of in vivo growth and protein-expression of Escherichia coli O157 strains in the bovine rumen

Previously, we had demonstrated that Escherichia coli O157:H7 (O157) strain 86–24 expresses proteins involved in survival rather than virulence in vitro in rumen fluid from dairy cattle limit fed a maintenance diet. Here, we verified if this observation would be true for different O157 strains grown in vitro in rumen fluid from, and in vivo in the rumen of, animals on contrasting maintenance (high fiber) and lactation (high energy-protein) diets usually limit fed to dairy cattle. For the in vivo studies, an economical, novel, reusable and non-terminal rumen-fistulated animal model permitting simultaneous evaluation of multiple bacterial strains in the bovine rumen was developed. All experiments were conducted in duplicate using different animals to account for host-related variations. The O157 strains included, 86–24, EDL933 and the super shed SS-17. E. coli Nal^R (#5735), derived from a bovine intestinal commensal E. coli, was included as a control. As expected, diet influenced ruminal pH and volatile fatty acid (VFA) composition. The pH ranged from 6.2–7.0 and total VFA concentrations from 109–141 μM/ml, in animals fed the maintenance diet. In comparison, animals fed the lactation diet had a ruminal pH ranging between 5.18–6.0, and total VFA of 125–219 μM/ml. Strain dependent differences in O157 recovery from the rumen fluid of cattle fed either diet was observed, both in vitro and in vivo, with O157 strains 86–24 and EDL933 demonstrating similar survival patterns. Analysis of the O157 proteomes expressed in the rumen fluid/rumen verified previous observations of adaptive responses. Any difference in the adaptive response was mainly influenced by the animal’s diet and growth conditions (in vitro and in vivo) and not the O157 strain. These new insights into the O157 responses could help formulate modalities to control O157 across strains in cattle at all stages of husbandry.

Derivatives of Esculentin-1 Peptides as Promising Candidates for Fighting Infections from Escherichia coli O157:H7

New strategies are needed to fight the emergence of multidrug-resistant bacteria caused by an overuse of antibiotics in medical and veterinary fields. Due to the importance of biofilms in clinical infections, antibiofilm peptides have a great potential to treat infections. In recent years, an increased interest has emerged in antimicrobial peptides (AMPs). One of the richest sources of AMPs is represented by amphibian skin. In the present work, we investigated the effects of two peptides derived from the frog skin AMP esculentin-1, namely, Esc(1-21) and Esc(1-18), on the growth, biofilm formation, and gene expression of the non-pathogenic Escherichia coli strain K12 and of enterohemorrhagic E. coli O157:H7. Both peptides showed minimal bactericidal concentrations ranging from 4 to 8 µM for Esc(1-21) and from 32 to 64 µM for Esc(1-18). They also, at sub-MIC doses, reduced the formation of biofilm, as supported by both microbiological assays and scanning electron microscopy, while they displayed no marked activity against the planktonic form of the bacteria. Transcriptional analysis in E. coli O157:H7 showed that both AMPs induced the expression of several genes involved in the regulation of formation and dispersal of biofilm, as well as in the stress response. In conclusion, we demonstrated that these AMPs affect E. coli O157:H7 growth and biofilm formation, thus suggesting a great potential to be developed as novel therapeutics against infections caused by bacterial biofilms.

Persistent Circulation of Enterohemorrhagic Escherichia coli (EHEC) O157:H7 in Cattle Farms: Characterization of Enterohemorrhagic Escherichia coli O157:H7 Strains and Fecal Microbial Communities of Bovine Shedders and Non-shedders

Cattle are carriers, without clinical manifestations, of enterohemorrhagic Escherichia coli (EHEC) O157:H7 responsible for life-threatening infections in humans. A better identification of factors playing a role in maintaining persistence of such strains in cattle is required to develop more effective control measures. Hence, we conducted a study to identify farms with a persistent circulation of EHEC O157:H7. The EHEC O157:H7 herd status of 13 farms, which had previously provided bovine EHEC O157:H7 carriers at slaughter was investigated. Two farms were still housing positive young bulls, and this was true over a 1-year period. Only one fecal sample could be considered from a supershedder, and 60% of the carriers shed concentrations below 10 MPN/g. Moreover, EHEC O157:H7 represented minor subpopulations of E. coli. PFGE analysis of the EHEC O157:H7 strains showed that persistent circulation was due either to the persistence of a few predominant strains or to the repeated exposure of cattle to various strains. Finally, we compared fecal microbial communities of shedders (S) (n = 24) and non-shedders (NS) (n = 28), including 43 young bulls and nine cows, from one farm. Regarding alpha diversity, no significant difference between S vs. NS young bulls (n = 43) was observed. At the genus level, we identified 10 amplicon sequence variant (ASV) indicators of the S or NS groups. The bacterial indicators of S belonged to the family XIII UCG-001, Slackia, and Campylobacter genera, and Ruminococcaceae NK4A21A, Lachnospiraceae-UGC-010, and Lachnospiraceae-GCA-900066575 groups. The NS group indicator ASVs were affiliated to Pirellulaceae-1088-a5 gut group, Anaerovibrio, Victivallis, and Sellimonas genera. In conclusion, the characteristics enhancing the persistence of some predominant strains observed here should be explored further, and studies focused on mechanisms of competition among E. coli strains are also needed.

Quantitative Microbial Risk Assessment of Listeria monocytogenes and Enterohemorrhagic Escherichia coli in Yogurt

Listeria monocytogenes can survive in yogurt stored at a refrigeration temperature. Enterohemorrhagic Escherichia coli (EHEC) has a strong acid resistance that can survive in the yogurt with a low pH. We estimated the risk of L. monocytogenes and EHEC due to yogurt consumption with @Risk. Predictive survival models for L. monocytogenes and EHEC in drinking and regular yogurt were developed at 4, 10, 17, 25, and 36 °C, and the survival of both pathogens in yogurt was predicted during distribution and storage at home. The average initial contamination level in drinking and regular yogurt was calculated to be −3.941 log CFU/g and −3.608 log CFU/g, respectively, and the contamination level of both LM and EHEC decreased in yogurt from the market to home. Mean values of the possibility of illness caused by EHEC were higher (drinking: 1.44 × 10⁻⁸; regular: 5.09 × 10⁻⁹) than L. monocytogenes (drinking: 1.91 × 10⁻¹⁵; regular: 2.87 × 10⁻¹⁶) in the susceptible population. Both pathogens had a positive correlation with the initial contamination level and consumption. These results show that the foodborne illness risk from L. monocytogenes and EHEC due to yogurt consumption is very low. However, controlling the initial contamination level of EHEC during yogurt manufacture should be emphasized.

Pathogenic E. coli from Cattle as a Reservoir of Resistance Genes to Various Groups of Antibiotics

Antimicrobial resistance has become a worldwide concern in all public health domains and reducing the spread has become a global priority. Pathogenic E. coli is responsible for a number of illnesses in humans and outbreaks in the past have been correlated with the consumption of contaminated bovine products. This is why surveillance in all the steps of production is essential. This study focused on identifying the pathogenic strains of E. coli in two large bovine abattoirs from Romania and France, and on associating them with the antimicrobial resistance patterns. A total of 250 samples from intestinal content were aseptically collected during the evisceration step of the cattle slaughtering process, from which 242 E. coli strains were isolated. Seventeen percent of all samples tested positive to at least one E. coli isolate carrying eaeA, stx1 and stx2 genes. The most prevalent genetic profile found in the E. coli strains tested was Stx1-positive and Stx2/eaeA-negative. More than 68% of the pathogenic E. coli isolated in Romania showed multi-drug resistance (MDR) and in France, the percentage was significantly lower (38%). The MDR profiles showed a high gene diversity for antibiotic resistance, which represents a great risk for environmental spread and human health. Our results indicate that in Romania, bovines can represent a reservoir for MDR E. coli and, hence, a surveillance system for antimicrobials usage in farm animals is highly needed.

The Importance of Shiga Toxin-Producing Escherichia coli O145:NM[H28]/H28 Infections in Argentina, 1998–2020

Shiga toxin-producing Escherichia coli (STEC) is known as a pathogen associated with food-borne diseases. The STEC O145 serogroup has been related with acute watery diarrhea, bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome (HUS). Argentina has the highest rate of HUS worldwide with 70% of the cases associated with STEC infections. We aimed to describe the epidemiology and genetic diversity of STEC O145 strains isolated across Argentina between 1998–2020. The strains isolated from 543 cases of human disease and four cattle, were pheno-genotipically characterized. Sequencing of five strains was performed. The strains were serotyped as O145:NM[H28]/H28, O145:H25, and O145:HNT, and mainly characterized as O145:NM[H28]/stx_2a/eae/ehxA (98.1%). The results obtained by sequencing were consistent with those obtained by traditional methods and additional genes involved in different mechanisms of the pathogen were observed. In this study, we confirmed that STEC O145 strains are the second serogroup after O157 and represent 20.3% of HUS cases in Argentina. The frequency of STEC O145 and other significant serogroups is of utmost importance for public health in the country. This study encourages the improvement of the surveillance system to prevent severe cases of human disease.

Occurrence of the Seven Most Common Serotypes of Shiga Toxin-Producing Escherichia coli in Beef Cuts Produced in Meat Processing Plants in the State of São Paulo, Brazil

ABSTRACT

Healthy cattle are considered the main reservoir of Shiga toxin-producing Escherichia coli (STEC) strains, so in some places in the world, products derived from beef are the most common source for disease outbreaks caused by these bacteria. Therefore, to guarantee that the beef produced by our slaughterhouses is safe, there is a need for continuous monitoring of these bacteria. In this study, 215 beef cuts were evaluated, including chilled vacuum-packed striploins (151 samples), rib eyes (30 samples), and knuckles (34 samples), from March to June 2018. These meat samples were collected from the slaughter of unconfined cattle, being arbitrarily collected from eight meat processing companies in São Paulo state, Brazil. Each sample was examined for the presence of STEC toxin type (stx1 and/or stx2 genes) and also the attaching and effacing E. coli (eae) gene, determined by a multiplex PCR assay. We show that the major seven STEC strains (O serogroups O26, O45, O103, O111, O121, O145, and O157) are not detected in any of the analyzed beef cut samples; however, three of them presented the virulence eae gene. Therefore, the absence of STEC strains in the beef samples may be an indication of the low prevalence of this pathogen in the cattle herd on the farm, associated with good hygiene and handling practices adopted by the meat industry.

HIGHLIGHTS

Improved Genomic Identification, Clustering, and Serotyping of Shiga Toxin-Producing Escherichia coli Using Cluster/Serotype-Specific Gene Markers

Shiga toxin-producing Escherichia coli (STEC) have more than 470 serotypes. The well-known STEC O157:H7 serotype is a leading cause of STEC infections in humans. However, the incidence of non-O157:H7 STEC serotypes associated with foodborne outbreaks and human infections has increased in recent years. Current detection and serotyping assays are focusing on O157 and top six (“Big six”) non-O157 STEC serogroups. In this study, we performed phylogenetic analysis of nearly 41,000 publicly available STEC genomes representing 460 different STEC serotypes and identified 19 major and 229 minor STEC clusters. STEC cluster-specific gene markers were then identified through comparative genomic analysis. We further identified serotype-specific gene markers for the top 10 most frequent non-O157:H7 STEC serotypes. The cluster or serotype specific gene markers had 99.54% accuracy and more than 97.25% specificity when tested using 38,534 STEC and 14,216 non-STEC E. coli genomes, respectively. In addition, we developed a freely available in silico serotyping pipeline named STECFinder that combined these robust gene markers with established E. coli serotype specific O and H antigen genes and stx genes for accurate identification, cluster determination and serotyping of STEC. STECFinder can assign 99.85% and 99.83% of 38,534 STEC isolates to STEC clusters using assembled genomes and Illumina reads respectively and can simultaneously predict stx subtypes and STEC serotypes. Using shotgun metagenomic sequencing reads of STEC spiked food samples from a published study, we demonstrated that STECFinder can detect the spiked STEC serotypes, accurately. The cluster/serotype-specific gene markers could also be adapted for culture independent typing, facilitating rapid STEC typing. STECFinder is available as an installable package (https://github.com/LanLab/STECFinder) and will be useful for in silico STEC cluster identification and serotyping using genome data.

AB5 Enterotoxin-Mediated Pathogenesis: Perspectives Gleaned from Shiga Toxins

Foodborne diseases affect an estimated 600 million people worldwide annually, with the majority of these illnesses caused by Norovirus, Vibrio, Listeria, Campylobacter, Salmonella, and Escherichia coli. To elicit infections in humans, bacterial pathogens express a combination of virulence factors and toxins. AB₅ toxins are an example of such toxins that can cause various clinical manifestations, including dehydration, diarrhea, kidney damage, hemorrhagic colitis, and hemolytic uremic syndrome (HUS). Treatment of most bacterial foodborne illnesses consists of fluid replacement and antibiotics. However, antibiotics are not recommended for infections caused by Shiga toxin-producing E. coli (STEC) because of the increased risk of HUS development, although there are conflicting views and results in this regard. Lack of effective treatment strategies for STEC infections pose a public health threat during outbreaks; therefore, the debate on antibiotic use for STEC infections could be further explored, along with investigations into antibiotic alternatives. The overall goal of this review is to provide a succinct summary on the mechanisms of action and the pathogenesis of AB₅ and related toxins, as expressed by bacterial foodborne pathogens, with a primary focus on Shiga toxins (Stx). The role of Stx in human STEC disease, detection methodologies, and available treatment options are also briefly discussed.

Antimicrobial susceptibility of Salmonella spp and Staphylococcus aureus isolated from beef sold in Campo Grande, Mato Grosso do Sul, Brazil

Abstract Hygiene failures in meat can be identified based on the evaluation of pathogenic microorganisms, which compromise the microbiological quality of food and can transmit food-borne diseases. The aim of the present study was to evaluate the hygienic quality of beef sold at supermarkets, butcher shops and public markets in the city of Campo Grande, state of Mato Grosso do Sul, Brazil, through the phenotypic and genotypic characterization of Salmonella spp. and Shiga toxin-producing Escherichia coli (STEC) as well as the investigation and quantification of Staphylococcus aureus. Seventy-one samples of beef from 17 commercial establishments were evaluated. Isolates were tested for antimicrobial susceptibility using the disk diffusion method recommended by the Clinical & Laboratory Standards Institute. Salmonella was found in 7.04% of the samples and 70.0% of the isolates were sensitive to the antimicrobials tested. A total of 25.35% of the samples were positive for Staphylococcus aureus, with counts ranging from 1.0 x 102 to 4.3 x 104 CFU/g; these isolates exhibited resistance to penicillin (87.5%), tetracycline (18.75%) and chloramphenicol (6.25%). None of the samples was positive for STEC. The detection of these pathogens in food poses a danger to public health, mainly due to the presence of antimicrobial-resistant isolates. These findings underscore the need for good hygiene and manufacturing practices at retail establishments.